Filtering apparatus

ABSTRACT

A filtering apparatus with a plurality of filtering elements ( 11 ) which can be accommodated in a filter housing ( 1 ) having a filter inlet ( 7 ) for fluid to be filtered and a filter outlet ( 9 ) for the filtered fluid, wherein during the filtration operation, at least one of the filtering elements ( 11 ) can be back-flushed by means of a back-flushing device ( 45, 49 ) in order to dedust the effective filtering surface of said filtering element, the back-flushing device comprising a pressure control device ( 19 ) for assisting the back-flushing operation, is characterized in that the pressure control device comprises a hydraulic accumulator ( 19 ), the one fluid chamber ( 47 ) of which can be filled during the filtration operation with a quantity of dedusted fluid and can be connected for a back-flushing operation via a back-flushing guide ( 45 ) to the clean side ( 29 ) of the filtering element ( 11 ) to be dedusted, and in that, for a back-flushing operation, a further fluid chamber ( 48 ) of the hydraulic accumulator ( 19 ) can be subjected to a gas pressure in order, by means of a resultant movement of the separating element ( 59 ) of the hydraulic accumulator ( 19 ), to at least partially again dispense the filling amount of the dedusted fluid for the back-flushing operation from the first fluid chamber ( 47 ).

The invention relates to a filtering apparatus having a plurality of filter elements, which can be accommodated in a filter housing having a filter inlet for fluid to be filtered and a filter outlet for the filtered fluid, wherein at least one of the filter elements can be backwashed by means of a backwashing device for cleaning its effective filter surface during the filtration operation, said backwashing device comprising a pressure control device for supporting the backwashing.

A filtering apparatus of the same generic type is disclosed in DE 10 2007 054 737 A1. Such a filtering apparatus permits a continuous filtration operation, wherein filter elements that are to be regenerated are backwashed one after the other, while the filtration is continued through the remaining filter elements, so that the filtration operation is not interrupted at any time.

With the known filtering apparatus, the backwashing operation does not take place exclusively in such a manner that the system pressure applied in the filtering apparatus allows a substream of the filtrate to flow through the filter element to be cleaned in the reverse direction during the respective backwashing phase in order to release the dirt from the filter element and discharge it, but instead a vacuum is created by means of a pressure control device on the respective filter element being backwashed in an effort to also remove even more stubborn soiling. Therefore, not only is the system pressure in effect for the backwashing but also a higher pressure gradient is available under the influence of the pressure control for releasing the soiling.

With the known filtering apparatus, the pressure control device has a cut-off element by means of which the fluid connection between the fluid to be filtered, flowing into the filter housing and the respective filter element to be backwashed can be cut off. This results in an interruption in flow in the case of the fluid flow entering the filter element before the backwashing operation, so that the velocity of flow prevailing in the cut-off operation causes a suction effect as a hydrodynamic effect. Therefore, not only is the system pressure available for the backflow of filtrate on the clean side of the respective filter element but also the backflow of filtrate is reinforced by the follow-up suction effect which is available because of the dynamic effect resulting from the cutoff of the flow entering from the dirty side.

However, the size of the hydrodynamic effect achieved by the cut-off process depends on the velocity of flow and therefore is limited accordingly. In areas of use where stubborn soiling that is difficult to release from the filter surface is to be expected, there is therefore the risk that the backwashing effect, which is hydrodynamically supported, is not completely satisfactory.

In view of these problems, the object of the present invention is to make available a filtering apparatus in which an especially effective backwashing effect, supported by pressure control, can be achieved.

According to the invention, this object is achieved by a filtering apparatus having the features of patent claim 1 as a whole.

One important feature of the invention is thus that the pressure control device has a hydraulic accumulator, in which its one fluid chamber can be filled with a quantity of cleaned fluid while the apparatus is operating in filtration operation and can be connected by means of a backwashing guide to the clean side of the respective filter element to be cleaned for a backwashing operation. In the case of a pressure application of the additional fluid chamber of the hydraulic accumulator, the resulting movement of the separation element of the hydraulic accumulator leads to ejection of the filling quantity of fluid, which reaches the filter element to be cleaned as flushing fluid by means of the backwashing guide.

Through the choice of the level of the gas pressure used in the hydraulic accumulator for the movement of the separation element, it is possible to optimally adapt the velocity of flow of the flushing fluid reaching the filter element through the backwashing guide to the given conditions, i.e., to select it so that the best possible flushing effect is achieved in adaptation to the type of filter medium. In particular in the case of relatively pressure-resistant filter elements such as conical or cylindrical slotted-sieve tube elements, it is possible to work with a high pressure level and thus with high velocities of flow in the hydraulic accumulator so that even stubborn soiling can be reliably released from the filter surface.

In advantageous exemplary embodiments, the additional fluid chamber of the hydraulic accumulator can be connected to a compressed gas source for the backwashing operation by means of a valve control device. In many cases, the use of compressed air may be especially advantageous, for example, when the filtering apparatus is operated in combination with installations or equipment in which a compressed air supply is provided.

The additional fluid chamber of the hydraulic accumulator for the backwashing operation can preferably be connected to a compressed gas source by means of a valve control device. In especially advantageous exemplary embodiments, the arrangement here is made so that a flushing gas tank situated outside of the filter housing is provided as the compressed gas source. Without any negative effect on the compactness of the filtering apparatus, a large gas volume kept on hand for the respective backwashing operations can thus be made available through a tank precharged with compressed air, for example.

The valve control device may have a fast-opening valve in a flushing gas line leading from the compressed gas source to the hydraulic accumulator in an especially advantageous manner. Due to a very rapid application of pressure, a greatly accelerated movement of the separation element of the hydraulic accumulator can therefore be achieved, so that a pressure surge is generated for the backwashing operation, thereby releasing even stubborn soiling from the filter surface.

A pneumatically operable diaphragm valve may advantageously be provided as a very fast-opening valve in the flushing gas line.

In especially advantageous exemplary embodiments, the hydraulic accumulator and backwashing guide are connected to one another and arranged in a rotatable manner in the filter housing, where they can be rotated by means of a rotational drive for adjustment movements between filtration operation and backwashing. Such an arrangement permits an especially simple and compact design in that a drive, preferably in the form of an electric geared motor is mounted on a readily accessible free end of the hydraulic accumulator; by means of this drive, the hydraulic accumulator can be adjusted to rotational positions in which the backwashing guide forms the fluid connection to the filter element to be cleaned.

In a particularly advantageous manner, the hydraulic accumulator may be a piston accumulator which can rotate about the cylinder axis together with the backwashing guide arranged on one end of the cylinder. In comparison with other accumulator deigns such as a diaphragm accumulator, a spring accumulator, a bellows accumulator or the like, the piston accumulator is characterized not only by a particularly robust design but also by a good ratio between design size and the capacity for holding cleaned fluid, which corresponds to the total displacement of the piston and thus corresponds approximately to the total volume of the accumulator cylinder.

In a particularly advantageous manner, the filter elements may be accommodated in their own element chamber. These element chambers are arranged in the filter housing on a circular line concentrically surrounding the cylinder axis. With this concentric arrangement, the connection of the individual element chambers to the rotatable backwashing guide can have a particularly simple design.

In a particularly advantageous manner, the hydraulic accumulator may be situated between the element chambers surrounding it in such a way that the fluid chambers of the hydraulic accumulator are located between the chamber connections of the element chambers situated at the ends of the filter elements. Such an arrangement in which the hydraulic accumulator is integrated between the respective inlet and outlet of the element chambers permits an especially compact design of the overall apparatus with an especially advantageous ratio between the required design height and the achievable size of the usable filter surface area.

In particularly advantageous exemplary embodiments, an input space having the filter inlet and forming the crude side in the filtration operation and a separate output space forming the clean side in the filtration operation and connected to the filter outlet are present in the filter housing between the hydraulic accumulator and the surrounding element chambers, the first space of which is connected to the chamber connection on the crude side and the second space of which is connected to the chamber connection of the element chambers in filtration operation on the clean side.

This arrangement may advantageously also be such that an overflow space connected to the clean side chamber connections of the element chambers is provided in the filter housing and is connected to the output space; in a rotational position of the hydraulic accumulator corresponding to the filtration operation, the first fluid chamber of this output space can be filled with cleaned fluid through a filling hole provided in the wall of the backwashing guide.

On the other hand, in other rotational positions of the hydraulic accumulator, which correspond to the backwashing of an element chamber, the backwashing guide is connected to the chamber connection of the element chamber to be backwashed on the clean side, so that a backwashing arm, which is arranged on the end of the cylinder of the hydraulic accumulator opposite the backwashing guide and which can be rotated together with the hydraulic accumulator, connects the chamber connection of the element chamber to be backwashed on the crude side to a backwashing line for the outflow of a backwashing quantity at the same time.

A motor-operated backwashing valve may be arranged in the fluid connection between the backwashing arm and the backwashing line, this preferably being a ball valve that can be rotated by means of a pneumatic drive.

The present invention is explained in greater detail below on a basis of exemplary embodiments depicted in the drawings, which show:

FIGS. 1A through 1C perspective oblique views of the filtering apparatus according to the invention, shown in simplified schematic diagrams in one embodiment having two or four or six filter element chambers;

FIGS. 2 and 3 perspective oblique views of the embodiment, drawn on a larger scale in comparison with FIG. 1, with six filter element chambers as seen toward the front side or the rear side of the apparatus;

FIG. 4 a central longitudinal section of the embodiment of FIGS. 2 and 3, illustrating the operating state of filtration operation;

FIG. 5 a longitudinal section corresponding to FIG. 4, illustrating the operating state of backwashing of the element chamber visible on the right side;

FIG. 6 a longitudinal section of a flushing gas tank assigned to the embodiments of the filtering apparatus shown here, drawn on a more enlarged scale in comparison with FIGS. 4 and 5, with the accompanying function components, and

FIG. 7 a longitudinal section of a diaphragm valve assigned to the flushing gas tank from FIG. 6, drawn here on a more enlarged scale in comparison with FIG. 6.

FIG. 1 shows an overall view of the filtering apparatus according to the invention in the partial FIGS. 1A through 1C shows a housing main part labeled as 1, filter element chambers labeled as 3 and a drive part labeled as 5. An inlet provided on the main part 1 for the supply of fluid to be cleaned is labeled as 7 and an outlet for cleaned fluid is labeled as 9. FIG. 1 also illustrates that the apparatus according to the invention can be designed in the manner of a modular building block system for operation with different numbers of filter elements. FIG. 1A shows an example having two filter element chambers 3, in which one filter element 11 (FIGS. 4 and 5) can be accommodated, while FIG. 1B shows an example with four filter element chambers 3 and FIG. 1C shows an example with six element chambers 3. Multiple filter elements 11 may also be provided in each element chamber 3 in the form of a so-called filter cartridge, for example, as is the case in the present embodiment.

FIGS. 2 and 3 show the embodiment of the filtering apparatus with six element chambers 3, with FIG. 2 showing the front side with the inlet 7 and the outlet 9, while FIG. 3 shows the opposite rear side, on which a flushing gas tank 13 is mounted. A diaphragm valve 15 which is connected to the flushing gas tank 13 is shown in an individual diagram in FIG. 7 and is pneumatically operable. A flushing gas line 17 is connected to the diaphragm valve 15; the apparatus can be supplied with pressurized flushing gas through this flushing gas line, as will be discussed in greater detail with reference to FIGS. 4 through 6.

Of these, FIGS. 4 and 5 each show a longitudinal section of the device, where FIG. 4 shows the operating state of the filtration operation, while FIG. 5 shows the condition in backwashing the filter element 11, which is in the element chambers 3 shown at the right of FIG. 5. As indicated most clearly in FIGS. 2 and 3, the element chambers 3 are arranged on a circular line so that they surround concentrically a hydraulic accumulator situated between them. As shown in FIGS. 4 and 5, the hydraulic accumulator is formed by a piston accumulator 19. As FIGS. 4 and 5 also show, an input space 21, which is connected to the housing inlet 7, and an output space 23, which is connected to the outlet 9 of the housing, are provided in the housing main part 1 between the element chambers 3 and the piston accumulator 19. The input space 21 is connected to the crude-side chamber connection 25 of the element chambers 3 in filtration operation (shown at the bottom of FIGS. 4 and 5). The output space 23 is connected to an overflow space 27 at the end, which is at the top in FIGS. 4 and 5, and the clean-side chamber connections 29 of the element chambers 3, which are in filtration operation are in turn connected to the output space, as shown in FIG. 4 which illustrates the status of the filtration operation. As indicated with dotted arrows 41 in FIG. 4, the unfiltered fluid from the input space 21 flows through the chamber connections 25 into the element chambers 3 and flows through the filter elements 11 from the outside to the inside, from which the filtered fluid then flows through the chamber connections 29 on the clean side to the overflow space 27, from which the filtrate flows to the output space 23, as indicated by the arrows 43, leaving this space through the outlet 9.

The piston accumulator 19 is rotatable about its cylinder axis between the input space 21 and the output space 23, wherein a sealed rotational bearing 31 is provided on a housing shoulder 33 separating the input space 21 from the output space 23. Another sealed rotational bearing 35 is situated on a bottom part 37 which seals the housing at the bottom. For adjusting the piston accumulator 29 to the desired rotational positions, the piston accumulator 19 is coupled by means of a driveshaft 39 to the drive part 5, which is an electric geared motor with an integrated rotational position sensor. As can be seen in particular with the rotational position of the piston accumulator 19 shown in FIG. 5, it has a backwashing guide 45 on the cylinder end at the top in the drawing, running cantilevered from the cylinder space 47 to the chamber connection 29 on the clean side of the element chamber 3 to be backwashed, which is the element chamber 3 visible on the right side in the diagram in FIG. 5. On the lower end of the piston accumulator 19, the latter has a backwashing arm 49, which has a similar cantilevered design like that of the upper backwashing guide 45 but extends from the chamber connection 25 on the crude side of the element chamber 3 to be backwashed to a backwashing output 51 for the discharge of the backwashing quantity with the entrained sludge. As indicated with the arrows 43, the backwashing quantity loaded with sludge goes through a backwashing valve in the form of a ball valve 53, which is rotatable by a pneumatic drive 55 to a backwashing line 57 and to an output flange 60.

During the filtration operation as illustrated in FIG. 4, the piston accumulator 19 is in a rotational position in which the backwashing guide 45 is not arranged on a chamber connection 29 of an element chamber 3 to be backwashed. In this operating state, filtrate flows out of the overflow space 27 and into the cylinder space 47 of the piston accumulator 19 through a filling hole 46 (FIG. 5) formed in the wall of the backwashing guide 45 and having a graduated diameter to form a narrow inlet opening, filling this cylinder space 47 while the piston 59 of the piston accumulator 19 moves downward into the position shown in FIG. 4. In this rotational position, which is shown in FIG. 4 and corresponds to the filtration operation, the cylinder space 48 situated on the bottom side of the piston 59 is vented because the input 61 of a feed channel 63 for flushing gas, which is visible only in FIG. 5, is in a corresponding position with a venting groove (not shown) in the bottom part 37 of the housing.

On the other hand, if the piston accumulator 19 is in the rotational position shown in FIG. 5 for a backwashing operation, the input 61 of the flushing gas channel 63 is connected to a flushing gas line 65 (see FIG. 6). To perform a backwashing, the piston 59 is driven upward by a supply of compressed air through the channel 63 to create a flow in the manner of a pressure surge from the filtrate in the cylinder space 47, thus creating a fluid flow that flows from the inside to the outside with a surge through the backwashing guide 45 and the chamber connection 29 on the clean side of the respective element chamber 3, flowing through the filter element 11 and thereby releasing the soiling, so that the backwashing quantity loaded with sludge goes through the chamber connection 25 to the backwashing output 51 and from there emerges through the opened ball valve 53 and the backwashing line 57. In the diagrams in FIGS. 1 and 2, the outlet flange 60 with the backwashing line 57 is shown lying on the front side of the apparatus but the entire backwashing output 51, including the ball valve 53, the backwashing line 57 and flange 60 may be arranged in any positions on the housing 1 as needed because there is no drive connection between the rotatable piston accumulator 19 and the backwashing output 51.

FIGS. 6 and 7 show details of the compressed gas supplied. As already mentioned and as shown in FIG. 3, a flushing gas tank 13 is mounted on the rear side of the apparatus. The flushing gas tank 13 can be filled with compressed air through a pressure line 67 with an upstream pressure regulating valve 69 and a cutoff valve 71, said compressed air being supplied to the cutoff valve 71 from a compressed air line 73, which contains a nonreturn valve 75. To supply compressed air as a pressure surge through the flushing gas line 65 to the piston accumulator 19 from the flushing gas tank 13, a fast-opening valve in the form of the diaphragm valve 15, which is pneumatically operable by means of a control line 79, is provided at a connection 77 of the flushing gas tank 13. The diaphragm valve 15 shown in greater detail in FIG. 7 is connected to the flushing gas line 65 by means of a connection sleeve 81. FIG. 7 shows the diaphragm valve 15 in the closed position in which the diaphragm 83 is held in the closed position against the pressure of the flushing gas tank 13 prevailing at the connection 77; it is kept in this position by a control pressure prevailing at the top side of the control space 85 situated in the diaphragm 83. In venting the control space 85, the diaphragm valve 15 opens quickly, so that the piston 59 of the piston accumulator 19 is moved suddenly for a backwashing operation by means of a compressed air pressure surge. 

1. A filtering apparatus having a plurality of filter elements (11), which can be accommodated in a filter housing (1) having a filter inlet (7) for fluid to be filtered and a filter outlet (9) for the filtered fluid, where at least one of the filter elements (11) can be backwashed for cleaning its effective filter surface by means of a backwashing device (45, 49) during the filtration operation, said unit containing a pressure control device (19) for supporting the backwashing, characterized in that the pressure control device includes a hydraulic accumulator (19) whose one fluid chamber (47) can be filled with a quantity of cleaned fluid during the filtration operation and can be connected to the clean side (29) of the filter element (11) to be cleaned for a backwashing operation by means of a backwashing guide (45), and an additional fluid chamber (48) of the hydraulic accumulator (19) can be acted upon by a gas pressure for a backwashing operation to dispense the quantity of fluid of the cleaned fluid at least partially from the first fluid chamber (47) for the backwashing operation by means of a movement of the separation element (59) of the hydraulic accumulator (19) thereby induced.
 2. The filtering apparatus according to claim 1, characterized in that the additional fluid chamber (48) of the hydraulic accumulator (19) can be connected to a compressed gas source (13) by means of a valve control device (15) for the backwashing operation.
 3. The filtering apparatus according to claim 1 or 2, characterized in that a flushing gas tank (13) situated outside of the filter housing (1) is provided as the compressed gas source.
 4. The filtering apparatus according to any one of the preceding claims, characterized in that the valve control device has a fast-opening valve (15) in a flushing gas line (65) leading from the compressed gas source (13) to the hydraulic accumulator (19).
 5. The filtering apparatus according to any one of the preceding claims, characterized in that a pneumatically operable diaphragm valve (15) is provided in the flushing gas line (65).
 6. The filtering apparatus according to any one of the preceding claims, characterized in that the hydraulic accumulator (19) and the backwashing guide (45) are connected to one another and are arranged rotatably in the filter housing (1) and can be rotated by means of a rotational drive (5) for adjustment movements between filtration operation and backwashing.
 7. The filtering apparatus according to any one of the preceding claims, characterized in that a piston accumulator (19), which can rotate about the cylinder axis together with the backwashing guide (45) arranged on one end of the cylinder, is provided as the hydraulic accumulator.
 8. The filtering apparatus according to any one of the preceding claims, characterized in that the filter elements (11) can be accommodated each in its own element chamber (3), these being arranged in the filter housing (1) on a circular line concentrically surrounding the cylinder axis.
 9. The filtering apparatus according to any one of the preceding claims, characterized in that the hydraulic accumulator (19) is arranged between the element chambers (3) surrounding it so that the fluid chambers (47, 48) of the hydraulic accumulator (19) are situated between the chamber connections (25, 29) of the element chambers (3) situated at the ends of the filter elements (11).
 10. The filtering apparatus according to any one of the preceding claims, characterized in that an input space (21) having the filter inlet (7) and forming the crude side in the filtration operation and an output space (23) which forms the clean side in the filtration operation and is connected to the filter outlet (9) are both situated in the filter housing (1) between the hydraulic accumulator (19) and the surrounding element chambers (3), the first space (21) thereof being connected to the chamber connection (29) on the crude side and the second space (47) being connected to the chamber connection (29) on the clean side of the element chambers (3) which are in filtration operation.
 11. The filtering apparatus according to any one of the preceding claims, characterized in that an overflow space (27) which is connected to the output space (23) and out of which the first fluid chamber (47) of the hydraulic accumulator (19) can be filled with cleaned fluid through a filling hole (46) situated in the wall of the backwashing guide (45) can be connected to the chamber connections (29) of the element chambers (3) and is situated in the filter housing (1).
 12. The filtering apparatus according to any one of the preceding claims, characterized in that the backwashing guide (45) is connected to the chamber connection (29) on the clean side of the element chambers (3) to be backwashed in the rotational positions of the hydraulic accumulator (19) which correspond to the backwashing of an element chamber (3); and a backwashing arm (49) rotatable together with the hydraulic accumulator (19) is situated on the end of the cylinder of the hydraulic accumulator (19) opposite the backwashing guide (45), said backwashing arm the chamber connection (25) on the crude side of the element chambers (3) to be backwashed to a backwashing line (57) for the outflow of a backwashing quantity.
 13. The filtering apparatus according to any one of the preceding claims, characterized in that the backwashing arm (49) can be connected to the backwashing line (57) by means of a motor-operated backwashing valve (71).
 14. The filtering apparatus according to any one of the preceding claims, characterized in that a backwashing valve in the form of a ball valve (71) is provided. 